Push-Back pallet rack systems are designed around the principle of organizing space by depth rather than width. This depth arrangement greatly increases storage density. Each bay can be loaded with the option of two to six pallets deep with each pallet stored on wheeled carts or trolleys that fit onto rails. The rails are slightly angled to take advantage of gravity. When a forklift places the pallet onto the cart, the forklift driver drives forward and causes the pallet to push the other pallets in the lane backwards.